Effect of strain on surface diffusion in semiconductor heteroepitaxy

We present a first-principles analysis of the strain renormalization of the cation diffusivity on the GaAs(001) surface. For the example of In/GaAs(001)-c(4x4) it is shown that the binding of In is increased when the substrate lattice is expanded. The diffusion barrier \Delta E(e) has a non-monotonic strain dependence with a maximum at compressive strain values (e 0) studied. We discuss the consequences of spatial variations of both the binding energy and the diffusion barrier of an adatom caused by the strain field around a heteroepitaxial island. For a simplified geometry, we evaluate the speed of growth of two coherently strained islands on the GaAs(001) surface and identify a growth regime where island sizes tend to equalize during growth due to the strain dependence of surface diffusion.Comment: 10 pages, 8 figures, LaTeX2e, to appear in Phys. Rev. B (2001). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm

STRUCTURE OF CLEAN III-V SEMICONDUCTOR SURFACES

Les structures atomiques de surfaces reconstruites de semiconducteurs III-V ont été résolues par la technique de diffraction des rayons X sous incidence rasante en ultra-vide pour deux orientations cristallographiques importantes : {111} et {001}. Il a été montré que dans le premier cas, le processus dominant la reconstruction est la rehybridation des orbitales tandis que dans le second, la dimérisation des atomes de la couche de surface est à l'origine de la nouvelle symétrie. La coexistence de deux structures ordonnées a été observée dans le cas de la reconstruction c(4x4) de GaAs (001) ce qui met en évidence le degré de liberté additionnel lié à une possible variation de la stoechiométrie de surface.The atomic structures of III-V semiconductor reconstructed surfaces have been solved by grazing incidence X-ray diffraction under ultra-high vacuum for two important cristallographic orientations : {111} and {001}. It was shown that the dominant effect in the first case was orbital rehybridization, whereas in the second example, dimer formation between the atoms of the surface layer is at the origin of the new symmetry. The coexistence of two ordered structures has been observed for the c(4x4) reconstruction of GaAs (001) which outlines the additional degree of freedom induced by a possible variation of the surface stoichiometry

Measuring surface stress discontinuities in self-organized systems with X rays

We have performed a grazing incidence x-ray diffraction study of the self-organized N/Cu(001) system. Diffraction satellites associated with self-organization are particularly intense around Bragg conditions of the bulk crystal. Bulk elastic relaxations due to surface stress discontinuities at domain boundaries are responsible for this feature. A quantitative analysis shows that these relaxations, computed by molecular dynamics or continuum elasticity, explain very well the whole diffraction study. A difference in surface stress of 7 N m-1 between uncovered and N-covered regions of the Cu surface is shown to be the driving force for self-organizatio

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International audienc

Bulk Dislocation Core Dissociation Probed by Coherent X Rays in Silicon

International audienceWe report on a new approach to probe bulk dislocations by using coherent x-ray diffraction. Coherent x rays are particularly suited for bulk dislocation studies because lattice phase shifts in condensed matter induce typical diffraction patterns which strongly depend on the fine structure of the dislocation cores. The strength of the method is demonstrated by performing coherent diffraction of a single dislocation loop in silicon. A dissociation of a bulk dislocation is measured and proves to be unusually large compared to surface dislocation dissociations. This work opens a route for the study of dislocation cores in the bulk in a static or dynamical regime, and under various external constraint

Heteroepitaxial growth of InAs on GaAs(100) mediated by Te at the interface

The heteroepitaxy of InAs on a Te covered GaAs surface is investigated by photoelectron spectroscopy. Core-level spectra probed with synchrotron radiation show that Te remains at the interface between InAs and GaAs in a concentration much higher than the solubility limit of this element in III-V compounds, suggesting that a new compound is being formed. We propose that this interlayer is responsible for the observed changing in the growth mode of the InAs overlayer from islands to layer by layer